Welcome to Bimmerfest -- The #1 Online Community for BMW related information! Please enjoy the discussion forums below and share your experiences with the 200,000 current, new and past BMW owners. The forums are broken out by car model and into other special interest sections such as BMW European Delivery and a special forum to voice your questions to the many BMW dealers on the site to assist our members!

Okay, story time! Skip past for condensed version Two days ago I noticed a small amount of white smoke coming out of my exhaust while idling at normal operating temperature. When revved in neutral, a fair amount of white smoke came out the exhaust, maybe 4 feet back before it dispersed. Naturally, I was concerned. Thought it could be a lot of water vapor or maybe burning oil since my PCV valve breather hose was missing and leaking oil. Took it for a thirty minute ride and, viola, white smoke gone no matter if idling or revving at high RPMs. The next morning I took it for a compression test, and even though it was cold there was no smoke or water vapor coming from the tailpipe on the drive there, couldn't replicate the smoke to show the mechanic no matter what. Ran a compression test out of curiosity, 210 all across the board except cylinder 6 which was sitting between 200-205. Replaced breather hose, intake vacuum hose and ICV line while I was there. We decided white smoke must have just been condensation. On the drive home a bit of smoke started coming out but once the engine was at operating temp it was not noticable from the drivers seat so I didn't think anything of it. Fast forward to today, drove a bit and no smoke. It was cold today, no water vapor either. Clean as a whistle. After work, about 45 degrees F outside, and you guessed it, white smoke same as before. Decent bit when idling, big cloud when revved in neutral at operating temperature. Checked my coolant, and guess what? Lost a good amount in one day! I know its relative to individual resevoirs, but it went down two notches in about 20 miles of city driving est. about 2- 4 ounces? Me and my dad agree the exhaust smoke smells faintly sweet, like coolant. The radiator was replaced about 35k miles ago, no noticeable leaks. Oil not visibly contaminated, remaining coolant not visibly contaminated. Oil filler cap clean as can be, smells like oil.

CONCLUSION: Guess I'll get a pressure test on the radiator tomorrow, see if there's any leaks. Any ideas what could be going on here? I've read sometimes a head gasket can be fractured but once the engine heats up, expansion causes the crack to close. Then overnight and at initial start up, coolant leaks until engine heats up. But even this doesn't explain why sometimes even at cold, exhaust won't smoke, and sometimes at normal temp exhaust will smoke?

Oh and I might add that there hasn't been even the slightest overheating problem. The needle steadily climbs to a hairline before the middle and sits there regardless of if I'm in stop and go traffic or on a straight road at moderately high revs ( 5000ish ). Heating and air conditioning work perfectly.

Is your coolant level dropping?
Best thing is to go to autozone or other and lend-a-tool the combustion leak test.
The fluid is cheap. Easy to use and it will tell if you have gasses in your coolant.
Which is the definition of a head gasket leak if I am not mistaken.

Yes, my coolant level is dropping. And I went to the local O'Reilly's and the guy looked at me like I was a space monkey when I asked if they had block testers. "You know, they check to see if you have hydrocarbons present in your radiator....little fluid, changes color?" Lol nothing, he almost acted like he didn't speak english. Freaking O'Reillys, if they weren't so close to my house I'd never shop there. I guess it'd be a good idea to head to autozone and do that before I pay for a pressure test on my radiator, cause I'm pretty sure there's no external leak. Thanks for the suggestion My525iT.

1. Do the pressure test anyway, but do not pay to pressure test your radiator. Purchase the kit from ebay...its roughly $40 shipped, which would be about the cost of getting it done professionally. You can keep it for life, its a good thing trust me.

2. I bet ebay has the block testing kit as well.

3. I suggest that you purchase a new rad cap and bleed screw even if the rad pressure test is successful...under $15 shipped in total. Its just insurance. You know, old car...

4. What is the colour of your coolant ? Does it have a good, strong smell (when you sniff the rad cap ) ? If it doesn't, please add cheap, strong smelling, brightly coloured coolant to your existing setup. I use 2 cans of coolant which cost $3.50 each. Being bright green, it is much easier to identify the source of leaks if they occur. Being strong smelling, if a hose should leak or burst especially while driving, the strong smell invades the cabin and alerts you to a problem up to 10 minutes before your engine actually begins to overheat. Remember the car buzzes when you leave the light on, but has no alarm when it is overheating. So this is a quick and dirty way to protect/alert yourself, especially if you do not intend to change all of your engine bay's coolant hoses to new ones. This is always recommended, the hoses themselves are not that expensive mayber $150 total for everything, but it is very troublesome job especially for the m50 engine.

5. Where are you coolant levels now ? How much are you losing daily ? Did you do any radiator flushes recently ? Did you change any hoses recently ? Often when this happens, air gets trapped in the system and is evacuated out to the expansion tank during driving, giving the impression that water levels are falling.

6. Keep monitoring your coolant levels daily until this is fixed or fully understood to be benign. Top up once it drops 2 marks below the cold level. Don't top up earlier.

7. I am sorry to post this and attempt to dominate this conversation even though I have owned fewer cars and am younger and more handsome than Snowy.

UPDATE: The coolant level from hell. When I first purchased the car, coolant level @ max line. A few days later, coolant level dropped to 2 notches below max line. A day later, coolant level dropped another 2 notches. Never added coolant, and posted this thread. All checks done at completely cold engine, for what it's worth. Few hours after I checked coolant level and discovered drastic drop, I check again. Engine slightly warm, and guess what? Coolant level shot back up to max line. WHAT THE EFF IS GOING ON?! I'm not insane, I've been checking at night and using a flashlight to illuminate coolant so I can tell precisely where it's at. I'm utterly confused...

And yes, it is strong smelling, bright green coolant. No external leaks noticeable, not a drop. Practically brand new radiator, I doubt the cap is leaking. I've looked at it while running at normal operating temperature, no gasses visible or heat shimmers coming from cap.

UPDATE: The coolant level from hell. When I first purchased the car, coolant level @ max line. A few days later, coolant level dropped to 2 notches below max line. A day later, coolant level dropped another 2 notches. Never added coolant, and posted this thread. All checks done at completely cold engine, for what it's worth. Few hours after I checked coolant level and discovered drastic drop, I check again. Engine slightly warm, and guess what? Coolant level shot back up to max line. WHAT THE EFF IS GOING ON?! I'm not insane, I've been checking at night and using a flashlight to illuminate coolant so I can tell precisely where it's at. I'm utterly confused...

I have a 1989 535, Mine does the exact same thing. Burns coolant every third or fourth blue moon. I cannot replicate it. Does not over heat, does not mix fluids. I have even given up on checking coolant because it doesn't ever seem to go down. The coolant resevoir isn't gunked up either. The car runs fine. no misses, I have had this issue sense Ive had it(3k miles now) Its a head gasket going really slow. Mine is cylinder 6 with the issue. I have had my car to 100 many times been to 120 once. I don't know how to blow it lol

Theres only two ways to burn coolant, cracked head or a gasket.

I would say your safe to drive it until your ready to do it. But I would never put off a head gasket if I cared about the vehicle.

READ RADIAN'S WRITE UP ON HEAD GASKET. It is amazing very well documented, And honestly if you care about your care thats how it should be done.

I have a 1989 535, Mine does the exact same thing. Burns coolant every third or fourth blue moon. I cannot replicate it. Does not over heat, does not mix fluids. I have even given up on checking coolant because it doesn't ever seem to go down. .

HG very small rupture, that comes and goes according to its expansion and contraction. Clearly not a showstopper, so I wouldn't bother with it either. However, would you like to try k-seal ? Its under $20 off ebay, is coolant friendly, won't gunk anything up, we've had it in an E36 m50 for a month now with no issues, and would probably fix this problem permanently if it was a HG issue.

If mechanics in a bottle actually work, and they do clearly work in many cases, then it is obvious that very sound chemical engineering is behind them. IOW this is technology. Hg leaks do not fix themselves even partially.

Which means you can and should use them in a car you intend to keep, where appropriate, and not doing so due to superstition is simply superstitous behaviour. Not all big problems in life need to have equally big and complex solutions to them.

UPDATE 2: Radiator shop down the street did a complimentary block check for me. Last night, smoke smelling like burnt coolant. This morning, no smoke, no smell. Fluid block tester was inconclusive, did not change color in the slightest. Test done at normal operating temp. Guess the next step will be to top the fluid off and keep an eye on everything. If it's a block issue, I'd rather ( obviously ) repair it sooner than later. But no way am I going to rip my engine apart if I'm not sure that's the problem. Any input?

Just to add to AMK's problem, I had a 91 525 M50 doing the same thing.

Same symptoms, AND overheating, froth under the oil cap and white smoke bellowing.
No oil contamination nor coolant contamination and 3 NON BMW mechanics telling me i
had a bad head gasket.

PITA for near 2 mos so I hardly used the car...
I called a buddy over. European car mechanic. Bled my system with the heater controls
on MAX DEFROST for reasons I can't fully explain and within an hour no more problems.
He told me when there's air in the system that HOT SPOTS can develop; areas where air
gets trapped and can burn off coolant, cause coolant loss and overheating.

His first and last advice... These cars are notorious for air in the cooling systems!
BLEED! BLEED! BLEED!

You have other problems in your car. Air in the block should have made it out to the rad's expansion tank through driving, if you had done normal bleeding to begin with. I would suggest that you change your thermostat and water pump (composite impellers only) if you have not done so recently.

UPDATE 2: Radiator shop down the street did a complimentary block check for me. Last night, smoke smelling like burnt coolant. This morning, no smoke, no smell. Fluid block tester was inconclusive, did not change color in the slightest. Test done at normal operating temp. Guess the next step will be to top the fluid off and keep an eye on everything. If it's a block issue, I'd rather ( obviously ) repair it sooner than later. But no way am I going to rip my engine apart if I'm not sure that's the problem. Any input?

It almost sounds as if you may have another issue like a bad fan clutch, wpump, tstat. Maybe the coolant is not circulating properly. These BMWs have there own way of running hot. Probably as Josh said you may be burning a tad of coolant at different times. My car has an OK head gasket but it drips on the outside and not through the internals. If you are losing coolant you may want to check the heater hose connections on the drivers side. 3 of them goes thru the engine bay to the foot well above the accelerator pedal behind the carpet/steering wheel. I am fixing one now - it sux because of the carpet.

Here is a link to help you understand and test your system. It is all in the Bentley but this is the best write-up I found to understand how the coolant circulates. http://www.bimmerboard.com/forums/posts/697674/
And NAPA also sells an additive you can add to coolant and use a blacklight to search for leaks.

My apologies if my post sounded like I was suggesting the
OP's problem was only bleeding. It was just MY personal experience.

Hi Tyrant,

From my experience, and I recently changed my radiator and was "losing" coolant for nearly 3 weeks, then for 1 week it was all cool, then I was "losing" coolant again, then it was all cool, then I've not lost more than an inch of coolant in 7 days.....I realise that a huge amount of air entered and stayed in the system during the rad change despite proper bleeding.

However, that huge amount of air slowly and eventually made its way out to the expansion tank. It has taken almost 1 month for that to happen.

My engine did not overheat at all due to this. I'm running without my fan clutch as well, and am just using my dual speed aux fan for primary cooling.

Your engine is the same as mine. It should not have overheated over this.

Air has a tendency to rise from the bottom of an engine to the top, more so for heated air. Air will be pushed around by fluid. Coolant is pushed around by the water pump, which pushes around the air, which eventually makes it out to the radiator and collects under the bleed screw etc. Water pressure is increased during driving, thus pushing water and trapped air around the system.

Many mechanics do not understand the nuances of our engines. Many enthusiasts understand the car far better than professional mechanics. This is the reason why more than one person has spent hundreds of dollars with mechanics and not solved problems, only to come to forums such as these and find the solutions, usually rather rapidly I might add.

Many mechanics misdiagnose the problem but solve it along the way while attending to something else. They are blind to what they have done in effect because well such is the power of their prior beliefs.

I understand that you feel that bleeding....sorry, BLEEDING....solved your problem. I am very sure that it did not. However, if I had not had this weird experience with my own radiator recently (which my mechanic confirms is typical when a new radiator is changed), I would have been tempted to agree with you. And, I might add, I changed my radiator when the engine was cold i.e. the thermostat should be nice and closed, which means no air should have entered the block from outside, and the cold bleed that I did should have sorted it out, and anything left over should have been settled by the hot bleeding I did later.

I was not there to see exactly what else your mechanic did that may have ended up fixing the problem. OR, the problem may have temporarily righted itself randomly. I know that is a unconvincing reason, but it has been known to happen. Coincidence is taken for correlation. I once had a thermostat stick open. I ran cold and normal for around one week. Then, it stayed normal for almost 8 months before this started happening again. Weird.

My original question to you remains unanswered. Did you recently change your thermostat ? Water pump ?